The present invention relates to fluid pressure regulators in general, and in particular to an improved fluid pressure regulator, that has at least two internal diaphragms to protect against harm from diaphragm failure.
Fluid pressure regulators find use in many industrial applications where the pressure of fluid supplied to a point of use must be regulated. Such regulators conventionally comprise a housing, in which a chamber is defined. A single diaphragm divides the chamber into two separate chambers, each in fluid sealed relationship from the other. One of the chambers receives fluid through a valved inlet connected to an external supply of fluid at an elevated pressure, and the fluid exits the chamber through an outlet. The other chamber may have an inlet for connection with an air signal at a predetermined pressure, and the fluid inlet valve connects with the diaphragm for being opened and closed in response to flexure of the diaphragm. Upon application of an air signal at the air chamber inlet, flexure of the diaphragm, in response to the opposing pressures of air and fluid in the chambers on opposite sides of the diaphragm, causes opening and closing of the valved inlet, in a manner to bring the fluid at the outlet to a pressure determined by the pressure of the air signal.
Such fluid pressure regulators often are used in industrial spray coating operations, where the pressure of paint or other material supplied to spray coating apparatus must be carefully controlled. For automatic spray coating operations, particularly where different colors of coating materials are sequentially supplied to the spraying apparatus, the pressure of the air signal usually is controlled by an electronic transducer. Color changing requires that the paint supply system, including the pressure regulator, be flushed with solvent between color changes, to clean it of one color of paint in preparation for supplying another. However, exposure to paint and solvent degrades and weakens the bellows of the pressure regulator, and repetitive cycling of the pressure regulator, during color changes, further weakens the bellows. Ultimately, the bellows may rupture and establish a path between the paint and air chambers, allowing paint and/or solvent to flow into the air chamber and through the air signal line to the electronic transducer. The result is destruction of the transducer and, if the paint and/or solvent are inflammable, creation of a fire and explosion hazard.